1. Field of the Invention
The present invention relates to fans and, more particularly, to a fan wheel.
2. Prior Art
There are many different types of fan blades known in the art. U.S. Pat. No. 2,023,111 discloses a silent fan with a complex fan blade shape. Another example can be seen in the U.S. Pat. No. 2,212,041 which discloses another type of fan blade with various surfaces having various different radii of curvature. There is a desire to provide a new type of fan wheel which is quieter than conventional fan wheels. There is also a desire to provide a new type of fan wheel which can rotate at a slower speed than conventional fan wheels, thereby requiring a smaller motor, but still providing the same air movement as a conventional fan wheel.
In accordance with one aspect of the present invention, an electric fan is provided having an electric motor and a fan wheel connected to the electric motor. The fan wheel has a hub and fan blades extending from the hub. The fan blades include a proximal section at the hub, a distal section and a middle section. The proximal section has a flat surface at a trailing edge of the blade. The trailing edge at the distal section is curved with an angle of curvature of about 10xc2x0. The trailing edge at the middle section is curved with an angle of curvature of about 36xc2x0. When the fan wheel is rotated by the electric motor at a constant speed, air pushed by each of the fan blades is propelled at a substantially same velocity and direction from the blade measured across a radial length of the blade.
In accordance with another aspect of the present invention, a fan wheel is provided comprising a center hub section; and blades extending from the center hub section. Each blade has a leading edge and a trailing edge. A section of the blade extending from the center hub section at the trailing edge has a forward facing substantially flat surface.
In accordance with another aspect of the present invention, a fan wheel is provided comprising a center section; and blades extending from the center section. Each blade comprises a first section proximate the tip, a second section, a leading edge along the first and second sections, a trailing edge along the first and second sections, and a tip at a junction of the leading and trailing edges. The first section is curved at the trailing edge with a first angle relative to a tangent to the trailing edge of between about 7xc2x0-13xc2x0. The second section is curved at the trailing edge with a second angle relative to a tangent to the trailing edge of between about 33xc2x0-39xc2x0.